[nrf fromtree] dts: mspi: Align op-mode binding with mspi.h enum

enum mspi_op_mode in mspi.h has different syntax to this binding.
Aligning these will allow for cleaner code in the implmented drivers.

Signed-off-by: David Jewsbury <[email protected]>
(cherry picked from commit 032ca4c)

Author: Hi-Im-David

dts/bindings/mspi/mspi-controller.yaml

@@ -22,8 +22,8 @@ properties:
   op-mode:
     type: string
     enum:
-      - "MSPI_CONTROLLER"
-      - "MSPI_PERIPHERAL"
+      - "MSPI_OP_MODE_CONTROLLER"
+      - "MSPI_OP_MODE_PERIPHERAL"
     description: |
       Indicate MSPI controller or peripheral mode of the controller.
       The controller driver may use this during initialization.